Fluid expansion power element



Dec. 4, 1962 J. SIR] 3,066,698

FLUID EXPANSION POWER ELEMENT Filed Feb. 2, 1959 JNVENTOR. laws .71509/.

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3,666,698 Patented Dec. 4, 1962 3,066,698 FLUID EXPANSION POWER ELEMENTLouis J. Siri, outh Bend, Ind., assignor to Penn Controls, Inc., Goshen,Ind, a corporation Filed Feb. 2, 1959, Ser. No. 790,463 3 Claims. (Ql.137-484) This invention relates generally to power element or diaphragmassemblies and in particular to a power element of simplifiedconstruction particularly adapted for ioifieration by thermal expansionof its liquid charge or As is well known, actuator elements of the typeherein disclosed are used extensively for actuation of switches or othercontrol apparatus which have application in the regulation of pressureand temperature in air conditioning, refrigeration and allied fields. InUS. Patent 2,942,- 624 issued to Arthur L. Good on June 28, 1960,titled, Pressure Responsive Actuator, and assigned to the as signee ofthe present invention, there is disclosed and claimed a power element ofthe type herein referred to. The present invention is embodied in asimplified and improved version of the power element described in saidcopending application.

It is an object of the present invention to provide a power element ordiaphragm assembly which is of a twopiece, simplified constructionlending itself to economical manufacture.

It is a further object of the present invention to provide a powerelement or diaphragm assembly constructed so that only a minimum volumeof the liquid charge is accommodated in the assembly, thereby minimizingthe effect of the temperature ambient to the power element on theresponse of the element to a temperature change at its remote bulb.

These and other objects will become apparent as the description proceedswith reference to the accompanying drawings in which:

FIG. 1 is an end view of a component of a power element embodying thepresent invention.

FIG. 2 is a side sectional View of the component shown in FIG. 1, thesectional view being taken along the line 22 of FIG. 1.

FIG. 3 is a cross-sectional view of a complete assembly embodying thepresent invention.

Referring to the drawings, there is generally indicated at a supportplate having a generally circular configuration and provided with arearwardly extending boss 11. The support plate has a central aperture12 therein which communicates with a passage 13 formed in the rearwardlyextending boss. A stem portion 14 extends from the boss 11 and may beutilized to mount the power element assembly in a control apparatus.Extending from the front face of the plate is an annular boss 16 formedintegrally with the plate. The circular area of the plate bounded by theboss is provided with intersecting, radial grooves 17 which communicatewith the aperture 12. Plate 10 extends somewhat beyond the annular boss16 to provide a peripheral ledge portion 18.

As may best be seen in FIG. 3, a flexible metallic diaphragm 19 overliesthe front face of the plate. The

diaphragm is formed at its peripheral margin so as to embrace the ledgeportion 18 of the plate and may be sealed thereto by any suitable meanssuch as soft solder or epoxy resin. The diaphragm is formed with asingle circumferential corrugation 21 which has a contour permitting thediaphragm to closely overly the annular boss 16 and be contiguoustherewith when unstressed as shown in FIGURE 3. A thrust pin oractuating element 22 has a disc-shaped portion 220: which is disposed incontiguous, overlying relation to the central area of the diaphragm. Itwill be understood that the thrust element 22 serves to transmit motionof the diaphragm to a switch arm or similar component of the controlstructure into which the power element is incorporated.

A capillary tube 23 may be soldered or otherwise secured to the boss 11so that its central bore communicates with the passage 13. It will beunderstood that the pressure chambers formed by the outer face of theplate 10 and the diaphragm is adapted to be filled by a pressuretransmitting fluid through the capillary tube 23. The remote end of thetube 23 (not shown) may be joined to a temperature sensing bulb, thecapillary pressure chamber and bulb providing a closed system containinga liquid having an appreciable thermal coefficient of expansion andserving to extend the diaphragm outwardly from the plate upon expansionof the liquid. It will be understood that the pressure chamber mayrespond to remote pressure changes rather than temperature changes inthe bulb, such pressure changes being transmitted to the chamber bymeans of a pressure transmitting fluid in the capillary, as is wellknown in the art.

In liquid expansion devices of the type herein described, under idealconditions, the movement of the thrust element 22 is directlyproportional only to a change in temperature at the remote bulb. Whenthe power element is formed so that it contains an appreciable amount ofthe actuating fluid, it will be evident that any change in thetemperature ambient to this retained fluid causes it to expand orcontract, thereby adding an increment of movement to the thrust elementwhich is independent of the temperature at the remote bulb. Such adevice thus responds both to the temperature at the remote bulb and tothe temperature ambient to the power element. In the present inventionthis undesirable response of the power element to the temperature at theelement itself is minimized. This feature is brought about by thepresence of the boss 16 which fills the space defined by the annularcorrugation in the diaphragm. The power element thus retains a minimumvolume of fluid and is responsive solely to temperature changes at theremote bulb.

The construction whereby the boss '16 closely underlies the corrugationin the diaphragm also permits the diaphragm to flex in the area of thecorrugation under pressure changes without bulging outwardly along itsperipheral margin.

The power element assembly described is of simplified construction andhas a minimum number of component parts thus lending itself toeconomical manufacture and assembly. While only a single power elementhas been described herein, it will be understood that the plate 10 mightbe formed so as to have corresponding annular bosses extending from itsopposite faces. Both faces of the plate might then be enclosed byflexible diaphragms, the resulting assembly thus providing a dual powerelement both of whose outer walls are flexible.

It will be understood that the invention herein described might bemodified and yet retain certain of its features. The scope of theinvention is therefore to be limited only by the appended claims.

The invention claimed is:

1. A pressure responsive actuator comprising a first rigid plate havinga circular configuration and a central aperture adapted to connect to apressure transmitting fluid filled capillary tube, an annular bossextending from one face of said first plate and integrally formedtherewith, said boss being disposed adjacent the marginal edge of saidplate, the portion of said first plate extending beyond said bossproviding an annular ledge, a flexible diaphragm overlying said one faceof the plate and sealed to said annular ledge thereof, said diaphragmhaving a single circumferential corrugation therein enclosing saidannular boss and contiguous therewith when unstressed,

the circular area of said diaphragm bounded by said corrugation closelyoverlying the central area of said first plate, and a second rigid platedisposed in contiguous, overlying relation to said circular area of thediaphragm, whereby the volume enclosed by said diaphragm and first plateis minimized while proportionally responding to the pressure of thepressure transmitting fluid and said corrugation is prevented frombulging as said diaphragm flexes in response to increased internalpressure.

2. A pressure responsive actuator comprising a first rigid plate havinga circular configuration and a central aperture adapted to be connectedto a pressure transmitting fluid filled capillary tube, an annular bossextending from one face of said first plate and integrally formedtherewith, said boss being disposed adjacent the marginal edge of saidplate, a flexible diaphragm overlying said one face of said first plateand sealed to the marginal edge thereof, said diaphragm having a singlecircumferential corrugation therein enclosing said annular boss andcontiguous therewith when unstressed, the circular area of saiddiaphragm bounded by said corrugation closely overlying the central areaof said first plate, and a second rigid plate disposed in contiguous,overlying relation to said circular area of the diaphragm, whereby thevolume enclosed by said diaphragm and first plate is minimized whileproportionally responding to the pressure of the pressure transmittingfluid and said corrugation is prevented from bulging as said diaphragmflexes in response to increased internal pressure.

3. A pressure responsive actuator comprising a first rigid plate havinga circular configuration and a central aperture adapted to be connectedto a pressure transmitting fluid filled tube, an annular boss extendingfrom one face of said plate and integrally formed therewith, said bossbeing disposed adjacent the marginal edge of said first plate, aflexible diaphragm overlying said one face of said first plate andsealed to the marginal area thereof, said diaphragm having acircumferential corrugation therein enclosing said annular boss andcontiguous therewith when unstressed, the circular area of saiddiaphragm bounded by said corrugation closely overlying the central areaof said first plate, and a second rigid plate disposed in contiguous,overlying relation to said circular area of the diaphragm, whereby thevolume enclosed by said diaphragm and said first plate is minimizedwhile proportionally responding to the pressure of the pressuretransmitting fluid and said corrugation is prevented from bulging assaid diaphragm flexes in response to increased internal pressure.

References (Iited in the file of this patent UNITED STATES PATENTS2,067,677 Farmer July 9, 1935 2,108,079 Schey et al Feb. 15, 19382,241,056 Chilton May 6, 1941 2,632,475 Elo Mar. 24, 1953

